1. Field of the Invention
The invention relates to a display device for a microwave surveillance system.
2. Description of the Prior Art
Due to the long wavelengths used in microwave surveillance systems, these systems were originally used only to detect the presence of large airborne targets. As the wavelengths become shorter the possibility of detecting ground targets was finally realized, although the scanning technique of using a scanned beam did not approach the maximum resolution of which these wavelengths are capable.
With the closing of the gap between radar frequencies and optical frequencies a considerable effort has been expended in extending the higher resolution optical target identification techniques to the microwave domain. One technique which is being used in the far infrared domain is the use of large arrays of detectors in the image plane of an optical lens system. Reflective type lenses or mirrors are used to avoid the frequency dispersion problems of refractive optics. Theoretically the ideal detector spacing is half a wavelength, easily achieved at microwave frequencies but difficult, if not impossible at optical frequencies. On the other hand the light quanta available at the optical detectors are more energetic and more numerous than at the microwave detector. This lower energy level makes it more difficult to convert the microwave image into a visible image.